Bilobate leaves of Bauhinia (Leguminosae, Caesalpinioideae, Cercideae) from the middle Miocene of Fujian Province, southeastern China and their biogeographic implications

Abstract

BackgroundMorphological and molecular phylogenetic studies suggest that the pantropical genus Bauhinia L. s.l. (Bauhiniinae, Cercideae, Leguminosae) is paraphyletic and may as well be subdivided into nine genera, including Bauhinia L. s.s. and its allies. Their leaves are usually characteristic bilobate and are thus easily recognized in the fossil record. This provides the opportunity to understand the early evolution, diversification, and biogeographic history of orchid trees from an historical perspective under the framework of morphological and molecular studies.ResultsThe taxonomy, distribution, and leaf architecture of Bauhinia and its allies across the world are summarized in detail, which formed the basis for classifying the bilobate leaf fossils and evaluating the fossil record and biogeography of Bauhinia. Two species of Bauhinia are described from the middle Miocene Fotan Group of Fujian Province, southeastern China. Bauhinia ungulatoides sp. nov. is characterized by shallowly to moderately bilobate, pulvinate leaves with shallowly cordate bases and acute apices on each lobe, as well as paracytic stomatal complexes. Bauhinia fotana F.M.B. Jacques et al. emend. possesses moderately bilobate, pulvinate leaves with moderately to deeply cordate bases and acute or slightly obtuse apices on each lobe.ConclusionsBilobate leaf fossils Bauhinia ungulatoides and B. fotana together with other late Paleogene – early Neogene Chinese record of the genus suggest that Bauhinia had been diverse in South China by the late Paleogene. Their great similarities to some species from South America and South Asia respectively imply that Bauhinia might have undergone extensive dispersals and diversification during or before the Miocene. The fossil record, extant species diversity, as well as molecular phylogenetic analyses demonstrate that the Bauhiniinae might have originated in the Paleogene of low-latitudes along the eastern Tethys Seaway. They dispersed southwards into Africa, migrated from Eurasia to North America via the North Atlantic Land Bridge or floating islands during the Oligocene. Then the genus spread into South America probably via the Isthmus of Panama since the Miocene onward, and underwent regional extinctions in the Boreotropics of mid-high-latitudes during the Neogene climatic cooling. Hence, Bauhinia presently exhibits a pantropical intercontinental disjunct distribution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0540-9) contains supplementary material, which is available to authorized users.

The Origin and Early Evolution of the Legumes are a Complex Paleopolyploid Phylogenomic Tangle closely associated with the Cretaceous-Paleogene (K-Pg) Boundary

“…Our results suggest extinction of stem-relatives of these two subfamilies, most likely related to Late Eocene and Oligocene cooling, and subsequent diversification of the crown groups during the Oligocene and Miocene, when both groups become diverse at several fossil sites (e.g. Wang et al, 2014;Lin et al, 2015;Poinar, 1991;Poinar and Brown, 2002).…”

A new species of Garcinia (Clusiaceae) from the middle Miocene of Fujian, China, and a phytogeographic analysis

“…Some studies of Fotan flora (Jacques et al, ; Lin et al, ; Shi et al, ; Shi & Li, ; Wang et al, ) supported a similar conclusion. The Garcinia leaves were found in a forest assemblage dominated by angiosperms, including species belonging to the families Dipterocarpaceae, Leguminosae, Moraceae, Urticaceae, and Euphorbiaceae, which have a high diversity in tropical to warm subtropical zones (Jacques et al, ; Lin et al, ; Shi et al, ; Shi & Li, ; Wang, Sun, Jin, Deng, et al, ). Combined with the Fagaceae and Lauraceae fossils, this finding indicates that the Zhangpu area should have had a warm and humid, tropical to subtropical climate during the depositional period of the Fotan flora.…”

“…Taking the ecological preference of G. tonkinensis into consideration, we can infer that G. zhangpuensis lived in a warm and humid tropical to subtropical and monsoonal climate, with a higher annual average temperature than the current temperature of Fujian. (Jacques et al, 2015;Lin et al, 2015;Shi et al, 2014;Shi & Li, 2010;. Combined with the Fagaceae and Lauraceae fossils, this finding indicates that the Zhangpu area should have had a warm and humid, tropical to subtropical climate during the depositional period of the Fotan flora.…”

Delineation of the selected Cucumis L. species and accessions using leaf architecture characters

“…Also, leaf lobes were noted to be essential to discriminate specific vein patterns and can display accurate homological and/or ancestral relationships (Viscosi and Cardini 2011;Inamdar and Shenoy 1982). Lobation and primary vein size were also some of the leaf characters served as basis for classifying the bilobate leaf fossils and evaluating the fossil record and biogeography of Bauhinia species (Lin et al 2015). It was observed that accessions with irregular secondary vein spacing were unlobed while those that have secondary vein spacing increasing towards the base were palmately lobed.…”